This invention relates to the art of apparatus for performing work on tubular metal workpieces and, more particularly, to improved apparatus for roll forming grooves in metal tubes or pipes.
Roll grooving apparatus is, of course, well known and, generally, includes a lower housing rotatably supporting a driven lower grooving roll, and an upper housing supporting a rotatable upper grooving roll matingly contoured with the lower roll so that a tubular workpiece therebetween is provided with a peripheral groove upon relative rotation of the grooving rolls and advancement of the upper roll towards the lower roll. Generally the lower roll is rotated by the drive motor of a power unit, and when a workpiece is interposed between the upper and lower rollers, the driven lower roller imparts rotation to the workpiece which in turn imparts rotation to the upper grooving roll, and the latter is gradually advanced towards the lower roll to progressively form the peripheral groove in the workpiece.
Heretofore, upward and downward displacement of the upper roll supporting housing has been achieved through the use of threaded feed screw arrangements between the upper and lower housings and which include a feed screw component capable of accommodating a tool such as a wrench for manually rotating the feed screw. Often, the upper and lower housings are inter-engaged for linear displacement of the upper housing toward and away from the lower housing, whereby it will be appreciated that considerable time is required to set up and to perform a roll grooving operation on a tube or pipe. In this respect, the feed screw must be manually rotated in the direction to separate the grooving rolls to facilitate the insertion of the end of a tube therebetween, and the feed screw must then be manually rotated in the opposite direction to bring the upper grooving roll into engagement with the outer surface of the workpiece. Often, the feed screw arrangement includes an adjustable stop to limit downward movement of the upper housing to control the depth of the groove which may vary from one workpiece to another depending on such factors as the diameter of the workpiece, the material of the workpiece and the wall thickness of the workpiece. Such an adjusting mechanism generally includes a threaded nut on the feed screw which is adjustably positioned therealong by manually rotating the nut, whereby it will be appreciated that further time is required to prepare the apparatus for a given roll grooving operation. Once the necessary adjustments are made, the lower grooving roll is driven to rotate the workpiece and upper grooving roll, and the feed screw is manually rotated in the direction to displace the upper housing towards the lower housing, thus to displace the upper grooving roll toward the lower grooving roll to progressively form the peripheral groove in the workpiece. When the desired groove depth is reached, driving of the lower grooving roll is stopped and the feed screw is manually rotated in the opposite direction until sufficient clearance is provided between the two rolls to accommodate removal of the grooved workpiece from therebetween.
In addition to the time required to perform a roll grooving operation, and the relatively inefficient manner of operation thereof, the time required to manually rotate feed screw arrangements for displacing the grooving rolls relative to one another can result in damage to the workpiece which renders the latter unacceptable and/or damage or undesirable wear on the component parts of the roll grooving apparatus which shorten the life thereof. More particularly in this respect, if any problems occur during the roll grooving operation it is impossible to quickly release the grooving rolls so as to preclude damage to the latter, damage to the workpiece, or the imposition of undesirable forces on the rolls and other component parts of the roll grooving apparatus which lend to damage or excessive wear thereof. For example, it is necessary for the workpiece to be properly aligned with the roll axes during a roll grooving operation so that the track of the groove is transverse to the workpiece axis. Misalignment at the beginning of the operation can cause the track of the groove to be spiral relative to the workpiece axis causing the workpiece to "walk" axially outwardly from between the grooving rolls. If the upper grooving roll is not displaced from the workpiece immediately, the workpiece can be damaged to the extent that the grooving operation cannot be completed so as to provide an acceptable end product, and/or the workpiece can drop off the end of the rolls and subject the operator to injury. While the power to the drive unit can be interrupted immediately, time is required for the momentum in the transmission to be overcome, whereby the improper tracking engagement with the workpiece does not immediately stop. Likewise, the undesirable tracking cannot be quickly stopped where displacement of the upper grooving roll from engagement with the workpiece requires manual rotation of a threaded feed screw, especially if the operator is using a ratchet wrench and has to first reverse the wrench drive and then begin the reverse rotation of the feed screw.
In other roll grooving apparatus heretofore provided, the upper grooving roll supporting housing is pivotally attached to the lower housing, but displacement of the upper housing toward and away from the lower housing is still accommodated through the use of a feed screw arrangement. Therefore, the time required to space the grooving rolls for the insertion of a workpiece therebetween, as well as the time required to perform a roll grooving operation, is basically the same as with apparatus in which the housing members are linearly displaceable relative to one another. Moreover, for the same reasons discussed above, the feed screw arrangement is unsafe from the standpoint of the inability to quickly release the grooving rolls or otherwise interrupt the roll grooving operation.
Other problems attendant to both of the foregoing feed screw type roll groovers result from the fact that considerable torque is required to be applied to the feed screw during a roll grooving operation and is applied by the operator by rotating the feed screw about a vertical axis. It will be appreciated that the force required to achieve such rotation results in the imposition of directional forces against the apparatus in a horizontal plane which tend to promote misalignment between the apparatus and workpiece. This in turn promotes "walking" of the workpiece, especially at the beginning of the roll grooving operation. Such application of horizontal directional forces is of further concern from the standpoint of operator safety because there is the potential for tipping the apparatus, especially when the directional force is lateral to the working axis. Moreover, the rotational force which must be applied to the feed screw by the operator promotes the latter's imbalance during a roll grooving operation which is both tiring and hazardous from the standpoint of operator safety.
In a manner similar to the latter roll grooving apparatus, it is known to provide a pipe or tube cutter with a cutter wheel pivotally mounted on a support member for displacement toward and away from supporting rollers. A workpiece to be cut is interposed between the supporting rollers and cutting wheel and, in a manner similar to that described above, the pivotally mounted cutting wheel is advanced toward the rollers and against the workpiece by a feed screw mechanism during relative rotation between the workpiece and the cutting apparatus. Thus, as with the similar roll grooving apparatus, it is not possible to quickly disengage the cutting wheel from the workpiece during a cutting operation should it become necessary or desirable to do so and, following the cutting operation, it is necessary to manually rotate the feed screw mechanism in the opposite direction to reset the cutting wheel for the next cutting operation.